A navigation apparatus provides a driver, who is unfamiliar with the local geography, with course guidance for travel from a departure point or present position to a destination in response to entry of departure point or present position and destination before travel starts. Many proposals relating to this navigation apparatus have been made in recent years.
FIG. 40 is a view for illustrating a prior-art example of a navigation apparatus.
As shown in FIG. 40, the conventional navigation apparatus is known to have a display system in which a map is displayed on a CRT screen and vehicle position 72, a course 71, a destination position 73 and paths of travel to the destination are displayed in a form superimposed on the map. Also known is a system, as disclosed in Japanese Patent Application Laid-Open No. 62-51000, in which an enlarged view of the vicinity of an intersection is possessed as image data and route guidance to the intersection is provided by displaying arrows.
However, a CRT screen for vehicles which displays a map from a present position to a destination is small in size, e.g., on the order of six inches. Consequently, when a large number of roads are displayed, particularly when travelling a long distance, it is difficult for the driver to tell which course to follow.
In addition, with an arrangement which displays a map showing only information from the point of departure to the destination, it is required that the map be prepared and stored in a memory unit in advance. Also, if there is an increase in the number of intersections at which turns are to be made, the map becomes difficult to read.
In a navigation apparatus, consideration has been given to a system in which guidance is provided at an intersection located at the point of departure, this guidance being the shape of the intersection, the orientation of landmarks and the name of the intersection displayed on a display screen by entering the number of the intersection located at the departure point. The road along which the vehicle is to proceed is indicated by a arrow on the diagram of the intersection. In accordance with this system, the driver identifies the pertinent intersection based on the displayed information. By entering "START" when the vehicle passes through the intersection, the driver is taught the present position and travel guidance starts.
With the foregoing system, however, the present position cannot be specified until the entry of present position ends; hence, the diagram of the intersection cannot be displayed in such a manner that the direction of travel will point from the bottom to the top of the display. Accordingly, in such case the diagram of the intersection generally is displayed with north being taken at the top of the screen. As a consequence, even if the vehicle is in the vicinity of the intersection, it is difficult for the driver to recognize on which road of the displayed intersection the vehicle is located. Further, when the direction of travel is indicated by an arrow display, as shown for example in FIG. 41, the arrow will point to the left if the vehicle is located above the intersection. As a result, the driver may misunderstand the display and turn in the opposite direction, namely left, when a right turn is to be made.
An arrangement has also been conceived in which intersection landmarks such as gasoline stations, banks and the like are included, and displayed, as image patterns in the image data indicating the vicinity of the intersection. However, if the diagram of the intersection is displayed with the direction of travel pointed toward the top of the screen, the intersection landmarks may be tilted or turned upside down and, hence, read incorrectly.
The present invention seeks to solve the foregoing problems and its object is to provide a display system in a navigation apparatus in which the required information is displayed in a form easy for the driver to read so that the information can be understood correctly in a short period of time.
Another object of the present invention is to provide a display system in a navigation apparatus in which, when an intersection at a point of departure is displayed, the diagram of the intersection is displayed in such a manner that the road at which the vehicle is presently located is shown below the departure intersection, namely in such a manner that the road leads to the intersection from below it.
A further object of the present invention is to provide a display system in a navigation apparatus in which intersection landmarks can be displayed on an intersection diagram in which the direction of travel points toward the top of the screen.